[boring_twenties]

Not FizzBuzz, and not me personally, but from someone I worked with and I have 0 reason to believe is lying:

After a few disappointing responses to better questions, interviewer decides to give a "freebie" and asks for a function that determines whether an integer is odd or even.

Candidate produces something that loops from 0 to the provided integer, incrementing two separate counters, then comparing them at the end.

Interviewer manages to stammer out something like "are you sure there isn't a more efficient way to solve this?"

Guy furrows his brow for a few minutes more, then a light bulb of sorts goes on, and he declares "Of course! ..."

"... I only need one counter!"

[Apocryphon]

That seems more like a failure of mathematical reasoning than in programming.

[kragen]

I would be amazed to meet someone who, if asked whether 3042041 was odd or even, would follow this exponential-time procedure manually. Unless the candidate was such a person, it's a failure of programming.

[Apocryphon]

They just seem numerically illiterate to the point of not realizing how to determine odds or evens.

Though perhaps, if they were more competent as a programmer, they would skip decimal math altogether and use the ol' bitwise operator trick.

[boring_twenties]

FWIW, gcc 10 generates identical code for `i % 2 != 0` and `i & 1 != 0` at -O1.

[kragen]

Yeah, but "doesn't know about the % operator" is a lot less damning than "can only think of an exponential-time algorithm to determine if a number is even". Like, this is terrible, but it's linear time:

    char s[32];
    sprintf(s, "%d", n);
    char c = s[strlen(s) - 1];
    return c == '0' || c == '2' || c == '4' || c == '6' || c == '8';